Signalling effect of NIR pulsed lasers on axonal growth.

In this work we show that a pulsed laser light placed at a distance is able to modulate the growth of axons of primary neuronal cell cultures. In our experiments continuous wave (CW), chopped CW and modelocked fs (FS) laser light was focused through a microscope objective to a point placed at a distance of about 15 microm from the growth cone. We found that CW light does not produce any significant influence on the axon growth. In contrast, when using pulsed light (chopped CW light or FS pulses), the beam was able to modify the trajectory of the axons, attracting approximately 45% of the observed cases to the beam spot. Such effect could possibly indicate the capacity of neurons to interpret the pulsating NIR light as the source of other nearby cells, resulting in extension of processes in the direction of the source.